Luis Rene Contreras

Delivery reliability, manufacturing capabilities and new models of manufacturing efficiency

Purpose – To provide a selective bibliography on reported empirical evidence regarding the compatibility/trade‐offs relationships between delivery reliability and other manufacturing capabilities, and also identify specific areas for future research.Design/methodology/approach – The paper conceptually examines published studies which have reported a trade‐off/compatibility situation between delivery reliability and other manufacturing capabilities such as internal quality, external quality, manufacturing costs, inventory costs, etc. Some different aspects of delivery reliability are also discussed.Findings – Principally, the paper identifies a need to study in more detail the different variables (manufacturing capabilities, contextual variables and manufacturing practices) that could be potentially associated with the achievement of high manufacturing efficiency (high levels of outputs/low levels of inputs) in terms of delivery reliability, materials inventory and safety resources.Research limitations/imp...

Test-retest reliability of Yale Physical Activity Survey among older Mexican American adults: A pilot investigation

The objective of the work reported in this paper is to assess test-retest reliability of Yale Physical Activity Survey Total Time, Estimated Energy Expenditure, Activity Dimension Indices, and Activities Checklist in older Mexican American men and women. A convenience-based healthy sample of 49 (42 women and 7 men) older Mexican American adults recruited from senior recreation centers aged 68 to 80 years volunteered to participate in this pilot study. Forty-nine older Mexican American adults filled out the Yale Physical Activity Survey for this study. Fifteen (12 women and 3 men) of the 49 volunteers responded twice to the Yale Physical Activity Survey after a 2-week period, and helped assess the test-retest reliability of the Yale Physical Activity Survey. Results indicate that based on a 2-week test-retest administration, the Yale Physical Activity Survey was found to have moderate (ρI = .424, p < .05) to good reliability (rs = .789, p < .01) for physical activity assessment in older Mexican American adults who responded.

Functional limitations in Mexican American elderly

Abstract This paper reports results of a study conducted to investigate the effects of age and gender of Mexican American elderly on the level of difficulty in performing household tasks (meal preparation, grocery shopping, house cleaning, laundry), personal tasks (dressing, bathing, grooming), transfer tasks (getting in and out of bed, getting in and out of chairs, getting in and out of bathtub, using stairs), and management tasks (using telephone, accessing mail, operating door locks). A questionnaire based on the Activities of Daily Living scale was constructed and administered to 62 Mexican American elderly subjects (31 males and 31 females) in Senior Centers in the City of El Paso. Their ages ranged from 65 to 84 (mean age: 74 years, SD: 6.2 years). Subjects quantified their responses to individual tasks as being 1 (task almost impossible to perform), 2 (possible with help), and 3 (easy and possible without help). In addition to summary statistics on responses for various tasks, a logistic regression was performed with age (continuous variable) and gender, as predictor variables, and responses to individual questions as the categorical ordinal response variables. Results show that age and gender both have significant effects on daily living tasks involving significant reaching, twisting and bending of trunk. To determine appropriate age separation at which difficulty levels in performing activities of daily living change, a discriminant analysis (with age groups in 10 year ranges, 65–74 and 75–84, and age groups in 5 year ranges, 65–69, 70–74, 75–79, 80–84) was performed on the responses. All predictor variables were used in the analysis. Results show that a 10-year age marker is a better discriminator of difficulty levels than a 5-year age range. Accommodating age related changes in functional abilities, and increasing functional independence of older adults will entail significant design modifications to products, systems and environments for daily use and living. Relevance to industry It is important for engineering designers, particularly, product designers, and engineers in the housing industry, to consider functional capabilities and limitations of elderly users when designing products of daily use, and daily living environments.

Daily living activities in older adults: Part I—a review of physical activity and dietary intake assessment methods

The aging process is expected to change advanced activities of daily living (such as employment and work activities), to basic activities of daily living (BADL; such as self-care activities, which is also considered work among older adults). In effect, older adults spend more energy on physical activities related to BADL, compared to heavy physical activity in any industrial work. Hence, accurate assessment of the type and extent of physical activity becomes critical for estimation of the activity metabolism, especially in older adults. Once an assessment of activity metabolism is made, energy balance can be quantified by comparing energy expenditure (including resting activity, and digestive metabolism) with caloric intake. Instruments and techniques available to quantify physical activity in older adults, and caloric intake in older adults are reviewed in this paper. The emphasis in this review is on questionnaire-based instruments that minimize burden on the investigator and the participant. Validity and reliability of the assessment instruments are also discussed. Relevance to industry Since most work activities requiring energy expenditure among older adults, especially retirees, consist of BADL, accurate assessment of activity metabolism and dietary intake is necessary for designing these work activities for older adults.

Integrating simulation modeling and equipment condition diagnostics for predictive maintenance strategies-a case study

This paper presents results from a case study in predictive maintenance at a distribution warehouse. A simulation model was built with ARENA/spl trade/ 5.0 for integrating predictive maintenance strategies with production planning strategies, for a conveyor system. Equipment health was monitored using condition-based parameters such as temperature and vibration for mechanical and electrical components such as rollers, electrical motors, and gearboxes. This diagnostic information was then integrated with a simulation model to simulate various equipment breakdown and failure conditions. Integration of condition-based monitoring of conveying equipment with a simulation model of the distribution system has provided a useful analytical tool for management to reduce production downtime due to unplanned maintenance activities - in this instance, downtime was reduced by more than 50% and work in process inventory was reduced by more than 65%.

Performance reduction in finger amputees when reaching and operating common control devices: a pilot experimental investigation using a simulated finger disability.

This paper reports results of an experimental laboratory investigation to determine if finger amputations (most pervasive upper extremity injury in the United States) result in significant work performance deterioration in tasks requiring operation of common control devices found in industrial settings. Ten male student volunteers from the University of Cincinnati participated in this study. The finger disability simulated was of an extreme nature, and was defined as the loss of four fingers in the preferred hand and the thumb in the nonpreferred hand. While being seated, participants activated 5 types of industrial control devices (a rotary dial, a push button, a toggle switch, a castor wheel, and a rocker switch). The controls were assembled on a device attached to a cylindrical pole, such that the control assembly could move up and down the cylindrical pole. The vertical height of control location (15, 20, and 30 in. from the seat reference point) and angle of control location in vertical plane (0°, 45°, 90°, and 135°) were varied in the experiment. Participants also had their torso restrained or unrestrained while reaching and activating controls, in addition to the presence or absence of the simulated disability in each participant. Functional reaches and arm reaches from the wall were measured for participants in the sample to determine the distances at which to place the control pole assembly. If a participant was able to reach the control, the time taken to activate and operate the control was recorded. Overall results indicate that participants took significantly longer (p < 0.05) to activate controls in the presence of the simulated disability. Physical restraint did not significantly alter performance provided the participant was able to reach the control. The type of control and the height of location of the control also significantly affected work performance.

Daily living activities in older adults: Part II—effect of age on physical activity patterns in older Mexican American adults

Abstract This paper, the second of a two-part paper, reports results from an experimental study conducted to understand physical activity patterns, and determine the effect of age on physical activity patterns in older Mexican American adults. The Yale Physical Activity Survey was administered to 49 older Mexican American adults (42 females and seven males), aged 68–80 years, recruited from senior recreation centers in the city of El Paso. Based on participant responses to questions about the type and duration of different types of physical activities, overall physical activity indices including the total time (h/week), the total energy expenditure (kcal/week), a summary index score, a vigorous activity score (units/month), a leisurely walking score (units/month), a moving score (units/month), and a standing and sitting score (both in units/month) were computed. These responses were then regressed with age (as the predictor variable). Since the number of older males in the study was small, data from men and women were combined. Results indicate that the standing score index ( p p Relevance to industry Understanding physical activity patterns (both work and leisure activities in daily living) in older adults is important for estimation of activity metabolism for among older adults.

Test-Retest Reliability of Functional Anthropometry and OARS Survey among Older Mexican American Adults

The aim of this study is to assess test-retest reliability of functional anthropometry measures and the Older American Resources and Services (OARS) survey among older Mexican American adults. A healthy sample of 30 Older Mexican American adults was selected from senior recreation centers. For functional anthropometry 20 variables were measured in the participants, and the participants were also asked to fill the OARS survey. All the participants responded to both the test again after two weeks and helped to assess the test-retest reliability of functional anthropometry measures and the OARS Survey. Pearson correlation analysis of the results indicates that the results of the anthropometric test and the OARS survey for the first administration and second administration were significantly positively correlated.

Comparative Analyses of Functional Reaches of Older Mexican American Adults

Older Mexican American adults have greater difficulty in performing activities of daily living (ADL) compared to other older adult groups. Differences in functional upper extremity anthropometry measures may help explain higher incidences of ADL difficulties among older Mexican American adults. Hence, as a first step, the objectives of this study were to compare baseline limiting outer fingertip and grip reaches of older Mexican Americans with published and available functional anthropometry data from other older adult groups. Older Mexican American females and males, aged 60–85+, recruited from Senior Centers in the City of El Paso, participated in the study. Stature, vertical fingertip and grip reaches, and horizontal fingertip and grip reaches, among other dimensions, were measured. Summary statistics, percentiles, and correlations between dimensions were generated for elderly Mexican American females and males. For overall comparison of Mexican American older adult anthropometry with other older adult groups, data available from several other studies in the Older Adult Data compendium was used. Overall comparisons of weighted means of available reach dimensions between older Mexican Americans and other older adult groups showed significant differences in most functional reach dimensions. Older Mexican American adults were found to have significantly different functional anthropometry than other groups.

Functional anthropometry and ranges of motion of older Mexican American adults

Among all older adult groups in the US, older Mexican American adults report the most functional limitation in activities of daily living. Upper extremity functional reaches and range of motion measures in older Mexican American adults may help explain their functional limitations and task performance in activities of daily living. However, there is little information on functional reaches and ranges of motion of older Mexican American adults, and how age and gender may influence their reach capability. Therefore, the objectives of this paper are to determine the effects of age and gender of older Mexican American adults on functional reaches and range of motion measures. Stature and 20 functional reaches and ranges of motion were measured in 250 (125 females and 125 males) older Mexican American adults recruited randomly from 3500 older Mexican American adults in a retired senior volunteers program. Regression analyses indicate that age and gender have significant cross-sectional effects on several important functional reaches and ranges of motion in older Mexican American adults. Insights on product design and living space considerations for older adults based on age-related functional performance changes are discussed.